1. Technical Field
The present invention relates to a liquid crystal device and an electronic apparatus.
2. Related Art
An existing TN (twisted nematic) liquid crystal device has a configuration such that liquid crystal is sealed between a pair of substrates, and an electric field is applied in a direction perpendicular to the surfaces of the substrates by means of electrodes formed on the substrates to control alignment of liquid crystal molecules and thereby modulates light transmittance ratio. In contrast, one type of liquid crystal device that attempts to increase the viewing angle is known, in which the direction in which an electric field is applied to liquid crystal is set in a direction substantially parallel to the surface of the substrate and the liquid crystal is rotated within a plane that is substantially parallel to the substrate using the electric field. In other words, this mode is configured so that a pair of electrodes are formed on one substrate to generate an electric field. As to the mode of this type, an IPS (in-plane switching) mode and an FFS (fringe-field switching) mode are known.
The FFS mode is a technology that is improved from the technology of the IPS mode. The difference in configuration is that the IPS mode has a pair of comb-shaped electrodes formed in the same layer, while, on the other hand, the FFS mode has a pair of electrodes formed in different layers. That is, the FFS mode is configured so that a comb-shaped electrode is formed above a solid electrode through an interlayer insulating film. Due to this difference in electrode structure, a direction of electric field generated slightly differs between the modes. The direction of electric field in the IPS mode is a horizontal direction in which electrodes are opposed to each other, while the electric field in the FFS mode, because electrodes are formed in different layers, has a strong electric field component in a vertical direction relative to the surface of the substrate particularly in proximity to the edges of the electrodes in addition to an electric field component in a horizontal direction. Note that Japanese Unexamined Patent Application Publication No. 2003-15146 describes the shape of an electrode which is one of examples of electrode used in the IPS mode; however, a pair of electrodes are formed in different layers, so that the direction of electric field is similar to that of the FFS mode.
As a result, in the regular IPS mode, even when liquid crystal molecules positioned between the electrodes are driven, liquid crystal molecules positioned just above the electrode are hardly driven. Thus, the electrode portions do not contribute to display, and these portions are screened by a light blocking film, so that the aperture ratio decreases. In contrast, in the case of FFS mode, not only liquid crystal molecules positioned between the electrodes, of course, but also liquid crystal molecules positioned just above the electrode are easily driven. Thus, in the FFS mode, when the electrode is formed of a transparent conductive film, it is possible for electrode portions to contribute to display to a certain degree. The FFS mode is advantageous in that it is possible to increase the aperture ratio in comparison with the IPS mode under the same condition.
Thus, it is effective to employ the FFS mode to attempt to increase the luminance of a liquid crystal device. Here, the switching element of a liquid crystal device uses P—Si (polysilicon) thin-film transistor (hereinafter, referred to as TFT) element, α-Si (amorphous silicon) TFT element, or the like. Then, when the P—Si TFT element is mainly used, a so-called overlayer structure in which an insulating film is formed so as to cover the TFT element, the surface is planarized, and an electrode is formed on the insulating film for driving liquid crystal. However, it is necessary to form a terminal for connection with mounting components such as a driving IC and a flexible substrate in the liquid crystal device.